C++ Niagra headers cannot be found - where? why? how?

	public MyGame(ReadOnlyTargetRules Target) : base(Target)
	{
		PCHUsage = PCHUsageMode.UseExplicitOrSharedPCHs;

        PublicDependencyModuleNames.AddRange(new string[] { "Core", "CoreUObject", "Engine", "InputCore", "HeadMountedDisplay", "NavigationSystem", "AIModule", "Niagara", "EnhancedInput", "UMG" });
		PrivateDependencyModuleNames.AddRange(new string[] {"Slate", "SlateCore"});
    }

You’ll notice Niagra is included in my public dependency. I have closed everything, reboot, regenerated, gone into the editor and confirmed Niagra is checked as a plugin. You name it.

I’ve done it.

However trying to include NiagraComponent.h and NiagraFunctionLibrary.h is impossible. I cannot find it anywhere.

What other step is missing to be able to use Niagra in C++?

The missing step is actually a missing letter: it’s Niagara, not Niagra.
You wrote it right in the dependencies though.